The present invention relates to improvements in winders of the type for winding a traveling web onto a roll.
One commonly utilized form of winder in the paper industry has been the two drum winder which has long been the workhorse of the paper industry. A two drum winder employs two parallel horizontal side-by-side drums with at least one driven in rotation to support and rotate a large roll being wound from a traveling supply web. An important factor in the performance in the two drum winder is the force or pressure between the winding drums and the roll being wound inasmuch as the tension of the web on the roll is a function of the nip pressure between the roll and the drums. Control of this factor has been obtained by using a rider roll which applies a downward force at the start of winding of the wound roll to increase the nip pressure between the drums and the roll being wound.
A significant problem resides in a two drum winder due to the fact that the caliper and basis weight profile varies along the length of a roll of paper being wound. This will generate irregularities along the roll length, and the roll is usually only supported at the high profile points by the drum. With the drums supporting the roll at the high points, the whole weight of the roll is supported at these locations thus creating high nip pressures and consequently high wound-in tensions, the degree of which depend on the width of the high points. One method of coping with this problem has been to oscillate the high points by oscillating the unwind stand making the high points wider.
It is accordingly an object of the present invention to provide improvements in winder structures and methods used for winding so that an improved quality of roll results and that the problems caused by high points in a roll being wound are substantially minimized, and the necessity for attempting to broaden the high points or otherwise control them is obviated.
A more broad object of the invention is to provide a drum or roll for effecting pressure contact with a roll being wound with a traveling web wherein the drum contacts the wound roll in area contact rather than point contact and wherein substantially uniform contact pressure is obtained between the drum and roll being wound over the length of the drum and high points on the wound roll do not adversely affect the contact pressure which remains distributed.
A further object of the invention is to provide an improved support roll construction for use in a two drum winder wherein the support roll conforms to irregularities along the length of the roll being wound and wherein a relatively broad surface contact is obtained at the nip between the drum and roll being wound.
A still further object of the invention is to provide a two drum winder with an improved deformable outer surface so as to provide surface area contact between the drum and roll being wound wherein the area of the nip widens at the weight of the roll increases and wherein the drum is particularly durable with a long operating life and has a constant circumferential length despite deformation at the nip.
A feature of the invention is to provide a support roll or drum for a winder such as where the drums in a two drum winder have a surface which comprises an inflatable sleeve reinforced so that the circumference is fixed and the profile straight. The drums are constructed with a resilient deformable outer surface so that the surface of the winder drum in its contact with the roll being wound deforms as tires on a car deform around a pebble while still providing uniform support for the car. The supporting drum includes an outer support surface layer formed of a deformable material surrounding an inflatable air chamber. In a preferred form, the air chamber is divided into individual chambers along the length of the supporting drum. The individual air chambers deform to match the profile of the paper surface along the roll being wound, thus creating more support for the whole weight of the roll and with more support, the pounds per square inch nip pressures become lower thus causing lower wound-in tensions. Also, as the weight of the roll builds up, the deformation of the air chamber will cause wider support or wider nip width thus automatically equalizing the pressure in the nip between the drum and the rolls. By controlling the pressures within the air chamber as a function of paper grade or desired results, different nip widths and softer or more controlled winding can be attained.
The deformable outer layer of the inflatable chamber preferably is of a material such as rubber with embedded nonextensible cords extending circumferentially such as at a small angle to the rotation of the drum surface. This maintains a constant circumference of the drum and provides a drum which is capable of transmitting torque to drive the roll in rotation. The embedded cords are high modulus cords which extend at a very low angle with respect to the circumferential direction. Very little rubber is provided on the outside surface to avoid flow. If a pattern is required for venting, very high modulus rubber is used. It is possible to use several such sleeves across the length of the drum, and the sleeves will have properties to conform to the varying profile of the roll of paper.
Other objects, advantages and features, as well as equivalent structures which are intended to be covered herein, will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments in the specification, claims and drawings, in which: